1. Field of Invention
This invention pertains to the proper dosimetry of UV light in clinical applications involving psoralen (e.g., PUVA therapy).
2. Related Art and Other Considerations
Psoralen concentrations in biological tissues are required for proper dosimetry of ultraviolet (UV) light in many clinical applications involving psoralen. As an example of one such application, PUVA therapy (Psoralen administration followed by Ultraviolet A irradiation) may prove effective in preventing restenosis of vessels following balloon angioplasty to open vessels narrowed by atherosclerosis. This technique relies on the ability of PUVA to cause crosslinks and monoadducts that prevent cellular proliferation without causing cell death. See, for example, U.S. patent application Ser. No. 08/041,001, filed Mar. 29, 1993 by Kenton W. Gregory, entitled "Inhibiting Vascular Smooth Muscle Cell Proliferation"; U.S. patent application Ser. No. 07/781,996, filed Oct. 23, 1991, by Kenton W. Gregory and R. Rox Anderson, entitled "Laser-Based Inhibition of Smooth Muscle Cell Hyperproliferation"; and U.S. Pat. No. 5,116,864 issued to March et al. (all of which are incorporated herein by reference).
Typically, the efficacy of PUVA therapy depends on the psoralen concentration and the UV dosage (e.g., the product of light dose and psoralen level). Variations in psoralen drug levels can lead to sub-optimal treatment.
Previous methods for determining psoralen levels are not real time determinations. Moreover, such methods are cumbersome for use in clinical PUVA applications and require elaborate equipment. Traditionally, such methods involve reverse phase liquid chromatography of blood serum. See, for example, Gasparro, F., et al., Journal Investigative Dermatology 90, 234-236, 1988. In such methods, the psoralen is physically separated from the tissue components and psoralen absorption is used to quantify levels of psoralen concentration.